Ethernet PHY mask fffffffb

Hi All

On a custom board that follows exact same ethernet design as beaglebone, i am observing the phy mask to be fffffffb.
(kernel 3.15 Robert’s kernel with path “cpsw: search for phy” applied)

I have read couple of threads but i could not exactly understand what can cause this mask to be fffffffb vs fffffffe.
Could anyone give any pointers for me to proceed?

The mdio driver show “driver unknown” and eth0 link never comes up.

Logs: snippet:

[ 3.982544] davinci_mdio 4a101000.mdio: davinci mdio revision 1.6
[ 3.988991] davinci_mdio 4a101000.mdio: detected phy mask fffffffb
[ 4.002317] libphy: 4a101000.mdio: probed
[ 4.006703] davinci_mdio 4a101000.mdio: phy[2]: device 4a101000.mdio:02, driver unknown
[ 4.015908] Random MACID = 3e:1d:66:06:26:f5

[ 11.348196] net eth0: initializing cpsw version 1.12 (0)
[ 11.423182] net eth0: phy found : id is : 0x7c0f1
[ 11.430055] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 18.727000] init: plymouth-upstart-bridge main process ended, respawning

root@arm:~# cat /proc/interrupts
CPU0
28: 1700 INTC 12 edma
30: 26 INTC 14 edma_error
33: 0 INTC 17 47400000.dma-controller
34: 1 INTC 18 musb-hdrc.0.auto
35: 1 INTC 19 musb-hdrc.1.auto
46: 0 INTC 30 4819c000.i2c
56: 0 INTC 40 4a100000.ethernet
57: 0 INTC 41 4a100000.ethernet
58: 0 INTC 42 4a100000.ethernet
59: 0 INTC 43 4a100000.ethernet
80: 5023 INTC 64 mmc0
84: 2435 INTC 68 gp_timer
86: 248 INTC 70 44e0b000.i2c
88: 1796 INTC 72 OMAP UART0
91: 0 INTC 75 rtc0
92: 1 INTC 76 rtc0
125: 0 INTC 109 53100000.sham
127: 0 INTC 111 48310000.rng
150: 0 GPIO 6 mmc0
IPI0: 0 CPU wakeup interrupts
IPI1: 0 Timer broadcast interrupts
IPI2: 0 Rescheduling interrupts
IPI3: 0 Function call interrupts
IPI4: 0 Single function call interrupts
IPI5: 0 CPU stop interrupts
IPI6: 0 IRQ work interrupts
IPI7: 0 completion interrupts
Err: 0